Top-fired ingot soaking pit and cover therefor

ABSTRACT

A COVER AND BURNER ARRANGEMENT FOR A TOP-FIRED INGOT SOAKING PIT WHICH EFFECTS IMPROVED CIRCULATION OF THE HEATED GASES, ESPECIALLY AROUND THE BUTTS OF THE INGOTS. THE BURNER DIRECTS THE FLAME TOWARD A PORTIN OF THE PIT COVER AT AN OBLIQUE ANGLE. THE COVER DIVERTS THE FLAME AND HEATED GASES DOWNWARDLY ALONG THE REMOTE END WALL OF THE PIT WITHOUT DISSIPATING THE VELOCITY OF THE GASES. THE REMOTE END WALL MAY ALSO BE PROVIDED WITH A SLOPING PORTION TO DIRECT THE DOWNCOMING GASES ACROSS THE FLOOR OF THE PIT.

United States atent [72] Inventor Harold L. Lloyd I 1,750,468 3/1930 Havman .1 263/43 Box 72, Winona, Ohio 44493 2,514,860 7/1950 Guthrie 263/40 [21] Appl. No. 821,022 2,572,819 10/1951 Schaefer... 263/40 [22] Filed May 1,1969 2,654,593 10/1953 Knight 263/40 [45] Patented June 28, 1971 FOREIGN PATENTS 632,778 12/1961 Canada 263/40 [54] TOP-FIRED INGOT SOAKING PIT AND COVER Primary ExaminerJohn J. Camby THEREFOR Attorney-Peter L Klempay 10 Claims, 12 Drawing Figs.

[52] US. Cl. 263140, e

0/173 ABSTRACT: A cover and burner arrangement for a top-fired In. i t ki it hi h effe t im roved circulation of the [50] Field of Search 263/40, 43; healed gases, especially around the n f h ingots. h 1 10/173 (A l; 266/5 (5) burner directs the flame toward a portion of the pit cover at an oblique angle. The cover diverts the flame and heated gases [56] References cued downwardly along the remote end wall of the pit without dis- UNITED STATES PATENTS sipating the velocity of the gases. The remote end wall may 1,296,122 3/1919 Roth 263/43 also be provided with a sloping portion to direct the 1,734,387 1 1/1929 Lykken 263/43 downcoming gases across the floor of the pit.

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PRIOR ART INVENTOR. HAROLD L. LLOYD AGENT PATENIEDJUNZMQYI 3588.062

SHEET 2 BF 3 INVENTC 'R. HAROLD L. LLOYD PATENTEU JUN28 lsn SHEET 3 OF 3 FIG.

FIG. IO

7 FIG.I2

FIG. 9

INVENTOR. HAROLD L. LLOYD AGENT TOP-FIRED INGOT SOAKING PIT AND COVER THEREFOR This invention relates to soaking pits such as are used in the steel industry for the heating of ingots and more particularly to a soaking pit construction which is characterized by improved circulation of the heated gases along the floor of the soaking pit.

When steel ingots are to be rolled into slabs or billets, they must first be heated to a uniform temperature. This heating is nonnally accomplished in a soaking pit which may, for example, be an open-top. refractory lined rectangular pit or chamber. The ingots to be heated are placed in a generally upright position within the pit and their lower ends rest on a layer of coke breeze or other granular material to protect the refractory lining of the pit floor. A nozzle is provided near the upper end of one of the pit walls through which a fuel, either liquid or gas, is introduced, surrounded by air for proper combustion. This mixture of air and fuel is projected at a high velocity into the pit where it burns in an elongated flame extending across the top of the pit. The ingots remain in the pit until they have reached the desired rolling temperature at which time they are removed and transferred to the rolling mill.

In order to properly roll steel ingots, it is necessary that each ingot be heated to a uniform temperature throughout and that all of the ingots in the pit, regardless of their location, be heated to the same temperature. These ideals are not accomplished in the soaking pits of the prior art as, in these pits, the heating flame is directed horizontally across the top of the pit and when this flame and the stream of hot gases strikes the opposite wall of the soaking pit violent turbulence is created in the gas stream and results in dissipation of the directional velocity of the hot gases which would otherwise promote circulation around the ingots. Consequently. during the heat up period in which the burner is firing at maximum capacity, the ingots furthest from the burner are heated more rapidly so that long periods of soaking at low inputs are required for uniform heating. Also, the lack of circulation of the hot gases contributes to the uneven heating of the individual ingots as their upper portions are in regions of considerably higher temperatures than are their lower ends. Since, in the prior art soaking pits, the flame is projected horizontally, there is the further danger that the upper portions of tall ingots will be subjected to excessive heating and that a portion of the steel of the ingots will be burned or "washed away.

It is the primary object of my invention to provide an improved soaking pit in which the stream of hot gases is circulated down the remote end wall and across the floor of the soaking pit. In accordance with the principles of my invention this is accomplished by providing a uniquely contoured soaking pit cover and by directing the incoming flame upwardly at an acute angle to the horizontal so that it strikes the cover at an oblique angle and is caused to move in a rapid stream down the end wall and across the pit floor.

It is also an object of the present invention to provide an improved soaking pit in which undesirable "washing" of the tops of the ingots within the pit is eliminated. Since the incoming flame and heated gases are directed toward the pit cover and then diverted to flow down the remote end wall and across the floor of the pit, the upper ends of the ingots are not subjected to overheating or to direct contact with the flame.

A further object of the invention is the provision of an arrangement for improving the circulation of hot gases within an ingot soaking pit which may be easily adapted to existing pits without necessitating extensive rebuilding thereof and which permits the heating of tall ingots in shallower pits than has heretofore been feasible. Since combustion occurs within the confines of the cover in the present invention rather than in the upper region of the pit itself as in the prior soaking pits, a greater portion of the height of the pit may be used advantageously. This is particularly desirable in view of the trend toward larger ingots and in existing installations where the pit cranes will not adequately serve deeper soaking pits.

The above and other objects and advantages of my invention will become apparent upon consideration of the following specification and the accompanying drawing wherein there is shown a preferred embodiment of the invention.

In the drawing:

FIG. I is a longitudinal cross-sectional view of an ingot soaking pit constructed in accordance with the principles of my invention.

FIG. 2 is a transverse sectional view taken along the line lI-ll ofFlG. 1;

FIG. 3 is a fragmentary longitudinal section of a modified soaking pit;

FIG. 4 is a longitudinal sectional view of a soaking pit constructed in accordance with the prior art;

FIGS. 5. 6, and 7 are longitudinal cross-sectional views of ingot soaking pits showing further modifications of the pit cover;

FIG. 8 is an inverted plan view of the pit cover of FIG. 9, showing the internal contour thereof;

FIG. 9 is a plan view of another embodiment of my invention employing a pair of high velocity burners mounted in the opposite end walls of the soaking pit; and

FIGS. 10, I1, and 12 are transverse sectional views of the pit cover of FIG. 9, taken along the lines X-X, Xl-XI, and XII-XII, respectively, of FIG. 9.

The soaking pit shown in FIGS. l and 2 is provided with a refractory lined bottom wall l0, refractory lined sidewalls 11, and refractory lined end walls 12 and 13. A protective layer of coke breeze or other granular material 14 may be provided on the bottom of the pit. Ingots 15 are placed within the pit with their lower ends resting on the coke breeze, preferably in an upright position of with their upper ends supported by the sidewalls II. A cover 16 is positioned over the pit, resting on the upper ends of the walls 11, I2, and 13. The upper surfaces of the walls may be provided with grooved tiles 17 which mate with tiles 18 secured to the cover 16. The cover 16 is formed of an outer metal shell 19 and a lining 20 of refractory material. As shown in FIG 2, the cover 16 is symmetric about its longitudinal axis. For a purpose to be described below the cover 16 has a high domed portion 21 adjacent the wall 12 of the soaking pit and a portion 22 slanting downwardly at a shallow angle from the domed portion 21 toward the wall 13 of the soaking pit.

A burner nozzle assembly 23 is mounted on the wall 13 of the soaking pit to project a flame into the pit through an opening 24 of the wall 13. The nozzle assembly 23 may be ofa type well known in the art in which a stream of fuel, either a liquid or gas, and a stream of air under pressure are projected through the opening 24 and into the soaking pit where the fuel and air mixture are burned. The nozzle assembly 23 and opening 24 are so positioned on the wall I3 that the centerline of the projected flame extends substantially parallel to the sloping portion 22 of the cover 16 and strikes the domed portion 2] at an oblique angle. A second opening 25 is also provided in the pit wall 13 and this opening communicates with a flue 26 to withdraw the products of combustion from the soaking pit.

When the ingots 15 have been positioned within the soaking pit and the cover 16 placed over and sealed to the pit, the nozzle apparatus 23 is operated to project a flame through the opening 24 into the pit. The burner may be operated to produce a velocity of approximately 300 fps. and it will be apparent that a rapid movement of the flame and heated gases occurs. The shape of the domed cover directs these rapidly moving gases so that a flow pattern is established within the soaking pit. As previously mentioned the incoming flame extends parallel to the slanted portion 22 of the cover 16. When the stream of hot gases strikes the cover in the region of the domed portion 21 these gases are directed downwardly by the curved end of the cover to flow in a rapidly moving stream down the wall 12 and across the bottom of the soaking pit. At the opposite end of the pit adjacent the wall 13 a portion of the gases escapes through the opening 25 to the flue 26 while the remaining portion of the gases are drawn upwardly by the incoming air and fuel mixture to unite with the flame and be redirected in the same circular pattern around the pit, It will be readily apparent that such a circulation pattern of the heated gases within the soaking pit produces more rapid heating of the butts of the ingots in the pit than do the prior art waking pits wherein severe turbulence of the gas streams is created when the stream of hot gases hits the remote wall of the soaking pit from a direction normal to the wall with a loss of directional velocity and movement of the heated gases across the pit floor.

To further improve the flow of gases through the soaking pit, the end wall 32 of the soaking pit remote from the burner and flue openings may be provided at its lower end with an inwardly stepped portion 33 having a sloping upper surface 34. The sloping surface 34 serves to divert the gases which have been directed downwardly by the domed portion of the pit cover so that these gases flow across the bottom 30 of the soaking pit toward the burner and flue openings. This arrangement prevents the development of any interruption of the rapidly moving gases at the lower corner of the pit remote from the nozzle.

The covers shown in FIGS. 5, 6, and 7 illustrate other cover contours which may be used to achieve the desired circulation path of the flame and heated gases. The soaking pit cover may have a horizontal surface 50 along a greater part of the length thereof and a sloping end portion 51 extending downwardly from the horizontal portion 50 to the lower edge of the cover. The sloping portion 51 is angled relative to the horizontal portion 50 of the cover in such a manner that the flame and gases projected upwardly at an acute angle from the horizontal by the nozzle 52 are first diverted by the horizontal portion 50 of the cover to the sloping portion 51 and then in a vertically downward path along the remote end wall of the soaking pit. The angle between the horizontal portion 50 and the sloping portion 51 of the pit cover necessary to achieve the desired vertically downward flow of the gases is given by the formula l/2(270 m where qlisthe angle between the horizontal portion 50 and the sloped portion 51 and 0 is the angle of inclination from the horizontal of the burner assembly axis.

FIG. 6 shows a further modification of the soaking pit cover in which there is provided a horizontal portion 60, a first sloping portion 61 extending downwardly therefrom and a second more steeply sloped portion 62 extending from the portion 6i to the lower edge of the cover. As in the previous embodimerits, the sloping edges 61 and 62 are so positioned relative to one another and to the horizontal surface 60 of the cover that the flame and stream of gases projected upwardly at an acute angle from the horizontal by the burner 63 strikes a surface 60 at an oblique angle and is deflected toward the surface 61 where it again strikes with an oblique angle. The surface 62 further deflects the stream of gases so that they flow downwardly along the remote wall of the soaking pit. In the embodiment shown in FIG. 7 the interior of the soaking pit cover 70 is contoured in a continuous curve having a uniform large radius. The center of the curvature and the radius are selected so that the flame and hot gases which strike the cover obliquely are deflected into the desired vertically downward path toward the bottom of the soaking pit. The side edges of the covers of the each of the embodiments may be vertical, sloped, as shown in FIG. 2, or curved as desired.

While only one nozzle opening and one flue opening have been shown in the wall 13 of the soaking pit, it will be readily apparent that additional nozzles and/or flue openings may be provided in this wall if desired. Such an arrangement is shown in FIGS. 8-1]. It should also be apparent that the concept of diverting the stream of gases into a downwardly moving flow along an end wall of the soaking pit and then across the pit floor by means of a contoured pit cover may also be advantageously applied to two-way fired soaking pits. In such pits nozzles 71 or 71 for projecting a stream of fuel and air into the pit are provided on opposite walls. The cover 73 for such a pit may be provided with a pair of sloped or contoured surfaces 74 and 75, one surface for each nozzle. and the flame and gases from each nozzle may be projected upwardly at an acute angle from the horizontal so as to strike the associated diverting surface of the cover obliquely. Thus, the stream of gases projected through the nozzle 71 strikes the contoured surface 74 while the stream of gases projected by the nozzle 72 strikes the contoured surface 75 and these streams are thus diverted downwardly to flow across the floor of the soaking pit in opposite directions. With such an arrangement, both streams of heated gases and combustion products are diverted downwardly and flow across the floor of the soaking pit thus heating the butt portions of the ingots and contributing to uniform heating of the ingots. It should also be apparent that the arrangement shown for effecting a seal between the cover 16 and the pit walls lll3 is illustrative only and that any suitable arrangement which provides a substantially airtight seal between these members may be employed.

It should now be apparent that the uniquely contoured soaking pit cover shown and described herein provides substantial improvements in the operation and efficiency of the soaking pit. By directing the incoming flame and stream of heated gases so that they strike the cover at an oblique angle and by so contouring the cover that the stream of gases is directed into a flow pattern down the wall and across the floo. of the soaking pit, a rapidly moving stream of hot gases is maintained around the ingots and particularly around the butts thereof. Unlike the prior art soaking pits, the velocity of the flame and gases is not dissipated when the gases strike the pit walls. Thus, my invention provides more rapid and uniform heating of the ingots. The possibility of burning or washing the top portions of the ingots is also eliminated as the flame is directed upwardly and does not strike the upper portions of any of the ingots in the soaking pit. The arrangement may be readily adapted to existing soaking pits by merely replacing the present cover with one contoured in accordance with the teaching of the present invention and by repositioning the burner assembly so as to direct the flame upwardly at an acute angle so that it strikes the pit cover obliquely. Since the contour of the cover provides additional volume in which combustion occurs above the tops of the ingots such an arrangement is particularly advantageous where it is desired to heat tall ingots and where it is not feasible to deepen the existing pits or where the existing pit cranes do not have the capacity to service deeper pits. In such an arrangement, the modification of existing soaking pits in accordance with my invention results not only in increased efficiency of operation but also in increased capacity of the soaking pit.

lclaim:

I. An ingot soaking pit having refractory lined bottom, side, and end walls; at least one burner assembly extending through one of the end walls for projecting a stream of fuel and air into said pit at a high velocity and an acute angle above the horizontal; and a removable refractory lined cover having tight fitting engagement with the upper surfaces of said side and end walls, the lower surfaces of the cover having a first region disposed generally at an acute angle to the stream of fuel and air and a second region extending from the first region in a generally inclined manner toward the pit end wall opposite the burner assembly, the first and second regions of the cover being oriented so as to direct the stream of fuel and air in a nonturbulent path across the cover, downwardly along the end wall opposite the burner assembly, and across the lower region of the pit.

2. A soaking pit according to claim I further characterized in that said cover is provided with a first sloping portion extending upwardly at an acute angle to the horizontal from the end of said cover adjacent said burner assembly, and a rounded portion extending from said first portion of said cover to the opposite end wall of said pit.

3. A soaking pit according to claim 1 further characterized in that said cover is provided with a first horizontal portion, said flame and stream of gases striking said first portion at an oblique angle thereto, and a second slanting portion extending downwardly from said first portion to the end of said cover adjacent said opposite end wall of said pit, the stream of gases deflected by said first portion being further deflected by said second portion to flow downwardly along said opposite end wall and across the floor of said pit.

4. An ingot soaking pit according to claim 3 further characterized in that the angle between said first and second ponions of said cover is given by the formula =%(2700) where is the angle between said first and second portions of said cover and 0 is the angle between the axis of the stream of gases and fuel projected by said burner assembly and the horizontal.

5. An ingot soaking pit according to claim 1 further including an inwardly projecting portion extending the length of said opposite end wall at the lower portion thereof, said inwardly projecting portion having a downwardly and outwardly sloping upper surface.

6. An ingot soaking pit according to claim 1 further characterized in that said ingot soaking pit is provided with a pair of burner assemblies mounted on opposite end walls of said pit; and said cover having a first portion contoured to divert the stream of gases projected by one of said pair of nozzles, and a second contoured portion to diver the steam of gases projected by the other of said nozzles, said first and second portions of sald cover diverting the respective streams of gases downwardly and across the floor of said soaking pit.

7. The method of firing an ingot soaking pit comprising: projecting at least one stream of fuel and air through a burner mounted in a wall of said pit into said pit at a high velocity; burning said stream of fuel and air within said pit; deflecting the stream of heated gases and combustion products down the wall of said pit opposite said burner; and further diverting said stream of gases and combustion products across the floor of said pit.

8. The method according to claim 7 further characterized in that said stream of fuel and gases is projected upwardly at an acute angle to the horizontal.

9. The method according to claim 8 further characterized in that a first stream of fuel and gases is projected into said pit from one wall thereof and a second stream of fuel and gases is projected into said pit from the opposite wall thereof, each of said streams of gases being deflected toward and across the floor of said pit.

10. The method according to claim 8 further characterized in that said stream of heated gases and combustion products strikes the cover of said pit at an oblique angle and is diverted downwardly by said cover without loss of velocity.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 588,062 Dated June 28, I971 Inventor(s) Hero] (1 L L] oyd It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

C1 aim col umn 5, l ine 8, fol I owing "formul a" insert Q and fol I owing "where" insert V) Cl aim 6, col umn 5, I ine 22 "diver" shoul d read d ive rt Signed and sealed this 2nd day of November 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTI'SCHALK Attesting Officer Acting Commissioner of Patents FORM PO-1D5O (10-69] USCOMM DC 60376 pfig U S GDVERNMINT PRINTING OFFICE 19.9 O-35i-J34 

